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Original Article
Volume 331:1037-1043 October 20, 1994 Number 16
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A Randomized Study of Coronary Angioplasty Compared with Bypass Surgery in Patients with Symptomatic Multivessel Coronary Disease
Christian W. Hamm, Jacobus Reimers, Thomas Ischinger, Hans-Jurgen Rupprecht, Jurgen Berger, Walter Bleifeld, for The German Angioplasty Bypass Surgery Investigation

 

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ABSTRACT

Background The standard treatment for patients with symptomatic multivessel coronary artery disease is coronary-artery bypass grafting (CABG). Percutaneous transluminal coronary angioplasty (PTCA) is widely used as an alternative approach to revascularization, but a systematic comparison of the two procedures is needed. We compared the outcomes in patients one year after complete revascularization with CABG or PTCA.

Methods A total of 8981 patients with multivessel coronary disease were screened at eight clinical sites, and 359 patients were randomly assigned to undergo CABG (177 patients) or PTCA (182 patients). Enrollment required that complete revascularization of at least two major vessels supplying different myocardial regions be deemed clinically necessary and technically feasible.

Results Among the patients in the CABG group, an average (±SD) of 2.2 ±0.6 vessels were grafted, and among those in the PTCA group, 1.9 ±0.5 vessels were dilated. After CABG, hospitalization was longer (median, 19 days, as compared with 5 for PTCA), and Q-wave myocardial infarction in relation to the procedure was more frequent (8.1 percent, as compared with 2.3 percent after PTCA; P = 0.022), whereas in-hospital mortality did not differ significantly between the two groups (2.5 percent in the CABG group and 1.1 percent in the PTCA group). At discharge 93 percent of the patients in the CABG group were free of angina, as compared with 82 percent of those in the PTCA group (P = 0.005). During the first year of follow-up, further interventions were necessary in 44 percent of the patients in the PTCA group (repeated PTCA in 23 percent, CABG in 18 percent, and both in 3 percent) but in only 6 percent of the patients in the CABG group (repeated CABG in 1 percent and PTCA in 5 percent; P<0.001). Seventy-four percent of the patients in the CABG group and 71 percent of those in the PTCA group were free of angina one year after treatment. Exercise capacity improved similarly in both groups. However, 22 percent of the CABG group, as compared with only 12 percent of the PTCA group, did not require antianginal medication (P = 0.041).

Conclusions In selected patients with multivessel coronary disease, PTCA and CABG as initial treatments resulted in equivalent improvement in angina after one year. However, in order to achieve similar clinical outcomes, the patients treated with PTCA were more likely to require further interventions and antianginal drugs, whereas the patients treated with CABG were more likely to sustain an acute myocardial infarction at the time of the procedure.

Patients with coronary artery disease who have persistent symptoms and a diminished quality of life while receiving medical therapy are generally considered for revascularization. Coronary-artery bypass grafting (CABG) and percutaneous transluminal coronary angioplasty (PTCA) are the most commonly used methods of revascularization for symptomatic coronary artery disease. In patients with multivessel disease, bypass surgery is the accepted and best-established treatment1. For patients with single-vessel disease, coronary angioplasty has become the standard treatment and has been shown to be more effective than medical treatment with regard to clinical symptoms2. In recent years, the application of angioplasty has been extended to certain patients with multivessel disease -- an approach stimulated by advances in balloon-catheter techniques and increased expertise in performing the procedure3,4,5,6,7,8,9,10,11. It was therefore deemed necessary to conduct randomized trials comparing PTCA and bypass surgery with respect to the clinical efficacy of the procedures and the long-term prognosis in patients with multivessel disease12.

The German Angioplasty Bypass Surgery Investigation (GABI) was a randomized study that compared the clinical efficacy of bypass surgery with that of balloon angioplasty in patients with symptomatic double- or triple-vessel coronary artery disease requiring complete revascularization.

Methods

GABI was a multicenter, randomized trial conducted at eight clinical sites in Germany where expertise in angioplasty meets the current standards13,14. The protocol was approved by the Hamburg Medical Board. Patients were recruited from July 1986 through December 1991.

Patient Selection and End Points

Patients under 75 years of age with symptomatic multivessel coronary disease (Canadian Cardiovascular Society [CCS] class >= II and stenosis >= 70 percent in diameter)15 were considered for enrollment. Revascularization of at least two major coronary arteries supplying different myocardial regions (the left anterior descending, left circumflex, and right coronary arteries) had to be clinically necessary and technically feasible according to the judgment of the local cardiologists and surgeons, based on clinical and angiographic criteria. Patients with totally occluded vessels (Thrombolysis in Myocardial Infarction [TIMI] grade 0) and lesions of the left main coronary artery (stenosis >30 percent in diameter) or equivalent lesions were excluded. In addition, randomization was precluded if more than approximately 50 percent of the left ventricular circumference would be in jeopardy should abrupt closure of one of the target vessels occur. Specific morphologic exclusion criteria included long lesions (>2 cm), diffuse peripheral coronary disease, and aneurysms. Patients with myocardial infarction during the previous four weeks and those who had previously undergone bypass surgery or angioplasty were not considered for enrollment.

The primary end point of the study was freedom from angina pectoris (CCS class <II) one year after the intervention. Secondary end points included the incidence of major cardiovascular events (death or myocardial infarction), procedure-related complications, and the rate of further interventions. The revascularization status and left ventricular function of the patients and the costs of the procedures were addressed in substudies.

Randomization was performed separately for each center by the use of random permuted blocks provided by the data center. Each patient had to give written informed consent before randomization. The data for each patient were recorded on special forms and mailed to the data center to be entered in a computerized data base. All patients with multivessel disease who were not randomly assigned to a treatment group because of exclusion criteria or an unwillingness to give informed consent were included in the study registry.

Intervention and Follow-up

The randomized patients entered the routine surgical or angioplasty program at each participating hospital. There were no requirements concerning technical details of the interventions or antianginal medications. All decisions during the interventions and follow-up period were left to the individual judgment of the treating physicians and those performing the procedures, in order to approximate current therapeutic practice. All angioplasty procedures were performed with standby surgical coverage.

A clinical history and physical examination were scheduled before the intervention, at the time of discharge from the hospital, and 3, 6, and 12 months after the intervention. These examinations included electrocardiography at rest and during exercise (modified Bruce protocol16), echocardiography, and routine blood tests. Coronary angiography was performed at the six-month follow-up visit.

The major complications documented in the study were death, myocardial infarction, bleeding that required transfusion, cerebrovascular events, pneumonia, and further interventions. Myocardial infarction was defined as the appearance of new Q waves on the electrocardiogram associated with the typical pattern of creatine kinase MB release (more than twice the upper limit of the normal range). The records of patients who died or had myocardial infarctions were cross-checked for validity by a critical-event committee at the data center. The CCS classification15 was used to grade angina pectoris. A detailed explanation of the classification and training in how to use it were provided to the study centers. Unstable angina was defined as angina at rest during the 24 hours preceding the intervention17.

Analysis of the coronary angiograms was performed by a central core laboratory (at the University of Mainz). Angioplasty was considered successful if the stenosis was reduced to less than 50 percent of the diameter of the vessel.

Statistical Analysis

The trial was designed to show that the two procedures (CABG and PTCA) are equally effective in maintaining freedom from angina one year after treatment. Assuming that freedom from angina (defined as a CCS class <II) can be achieved in approximately 65 percent of patients after CABG,18 we determined that, from the clinical point of view, the two procedures could be considered therapeutically equivalent if the success rates for the two treatment groups did not differ by more than 15 percent. Fixing the type I error at 5 percent and the type II error at 20 percent, we calculated that a sample size of 400 patients was necessary (200 for each group)19.

All data were analyzed according to the original randomization groups (intention-to-treat analysis). Quantitative data are expressed as means ±SD or as medians with the lower and upper quartiles given if the distribution is skewed. For the comparison of continuous variables, appropriate t-tests or nonparametric tests (the Mann-Whitney or Wilcoxon test) were used20. For nominal or categorical data, significant differences between the two treatment groups were calculated with the contingency-table test (Halton-Freeman21 and Fisher20). For the primary end point (freedom from anginal symptoms), the 95 percent confidence intervals for differences between the two groups were calculated20. Differences in major cardiac events were evaluated with the log-rank test20. Differences between the groups were considered significant if the P value was less than 0.05 for a two-tailed test.

Results

Enrollment and Randomization of Patients

A total of 8981 patients with multivessel coronary disease were screened; 8622 patients (96 percent) did not meet the clinical or angiographic requirements for inclusion or refused to give informed consent. Forty-four percent of these had double-vessel disease, and 56 percent had triple-vessel disease. One third of the patients could not be randomized because of specific protocol restrictions (23 percent had previously undergone PTCA or CABG, and 10 percent had had recent myocardial infarctions). In the other patients the coronary features were unsuitable (35 percent had total coronary occlusions, 17 percent had lesions of the left main coronary artery or equivalent lesions, and 8 percent had large areas at risk). Two percent of the patients refused to participate in the study. The recommended treatment for the patients who were not enrolled was bypass surgery in 53 percent, angioplasty in 15 percent, and medical therapy in 32 percent.

Enrollment was prematurely terminated after 359 patients had been randomly assigned to treatment, because an interim statistical analysis showed that the two treatment groups did not differ in regard to the primary end point. Randomization resulted in the assignment of 177 patients to bypass surgery and 182 to angioplasty. The two treatment groups did not differ significantly with respect to base-line characteristics (Table 1).

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  		Table 1. Base-Line Characteristics of 359 Patients with Multivessel Coronary Disease Randomly Assigned to CABG or PTCA.

 
Treatment Outcomes

In the interval between randomization and intervention (median, 53 days for the CABG group and 19 days for the PTCA group), 5 patients died (4 in the CABG group and 1 in the PTCA group), and 17 patients withdrew their consent to participate in the study (12 in the CABG group and 5 in the PTCA group). A total of 337 patients (94 percent) actually underwent the assigned treatment.

Among the 176 patients undergoing PTCA, an average of 1.9 ±0.5 vessels per patient, or a total of 335 vessels, were dilated. The distribution of revascularized vessels is shown in Table 2. Complete revascularization was achieved in 86 percent of the patients. PTCA was performed as a staged intervention (with angioplasty procedures performed over more than one day) in 30 percent of the patients. Angioplasty was successful (<50 percent residual stenosis) in 92 percent of all treated lesions. Emergency bypass operations the same day were necessary in five patients (2.8 percent). Ten additional patients (5.7 percent), in whom PTCA was uncomplicated but not successful, were referred for elective CABG during the initial hospitalization, and five patients required repeated PTCA before discharge. Four patients had Q-wave myocardial infarctions (2.3 percent), and one of the four died. Two patients (1.1 percent) died during hospitalization, one of them within 24 hours after PTCA (Table 3).

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  		Table 2. Treated Vessels in the Two Groups of Patients.

 
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  		Table 3. Complications and Events during Hospitalization.

 
Among the 161 patients undergoing CABG, an average of 2.2 ±0.6 vessels per patient, or a total of 351 vessels, were grafted. The internal thoracic artery was used for grafting in 37 percent of the patients. During the initial hospitalization, two patients required repeated surgery for coronary revascularization, and one additional patient underwent PTCA. Six other patients required repeated thoracotomy for reasons other than revascularization. In addition, surgery was complicated by strokes in two patients (1.2 percent) and by a pulmonary embolism in one (0.6 percent). The rate of postoperative pneumonia was higher in the CABG group than in the PTCA group (10.6 percent and 1.1 percent, respectively; P<0.001), and the rate of perioperative Q-wave infarction (8.1 percent) was also higher in the CABG group (P = 0.022) (Table 3). Four patients (2.5 percent) died during hospitalization, one of them within 24 hours after the operation. Two of these patients died after perioperative infarctions. There was no significant difference in mortality between the two treatment groups (Table 3 and Table 4).

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  		Table 4. Major Events and Further Interventions in the Two Treatment Groups.

 
The median hospital stay was 5 days (upper and lower quartiles, 3 and 10) after PTCA and 19 days (14 and 24) after CABG. Both procedures were effective in relieving angina at the time of discharge (Figure 1). However, freedom from angina (CCS class <II) was achieved in 93 percent of the CABG group but in only 82 percent of the PTCA group (P = 0.005). No patient in the CABG group and only 5 percent of the patients in the PTCA group continued to have CCS class III angina.


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  		Figure 1. Percentage of Patients with Angina at the Time of Randomization and Discharge and 6 and 12 Months after Undergoing Treatment with CABG or PTCA.

 
Clinical Follow-up

Clinical follow-up data for one year were available for 139 patients in the CABG group and for 155 in the PTCA group. After discharge, one patient in the CABG group died of injuries caused by a car accident, and one patient in the PTCA group died during elective bypass surgery (in the seventh month of follow-up). There were no myocardial infarctions in the CABG group after discharge, but Q-wave infarctions occurred in three patients in the PTCA group (P = 0.249). The cumulative risk of death or myocardial infarction from the time of randomization was 13.6 percent in the CABG group, as compared with 6.0 percent in the PTCA group (P = 0.017, by the log-rank test). If only the patients who underwent the assigned treatment are included in the analysis, major events were still more frequent in the CABG than in the PTCA group (P = 0.047).

Both treatments were highly effective in relieving angina (Figure 1). At the three-month follow-up visit, freedom from angina (CCS class <II) was reported by 84 percent of the patients in the CABG group, as compared with 60 percent of those in the PTCA group (P<0.001). However, this difference disappeared with further follow-up. At 12 months, 74 percent of the patients in the CABG group and 71 percent of those in the PTCA group were free of angina. The mean (±SD) difference in the proportions of patients in the two groups who were free of angina after one year was 3.0 ±10.4 percent (95 percent confidence interval, -7.4 to 13.4 percent). Class III or IV angina was present in only 7 percent of the patients randomly assigned to CABG and in only 8 percent of those randomly assigned to PTCA (P = 0.82).

The symptomatic benefit was accompanied by an improved capacity for exercise. The results of paired treadmill tests conducted after 12 months were available for 111 of the patients in the CABG group (80 percent) and for 127 of those in the PTCA group (82 percent). The median workload increased from 350 to 475 watt-minutes (watts times minutes) (P<0.01) in the CABG group and from 375 to 450 watt-minutes (P<0.01) in the PTCA group. The median change in the workload was 75 watt-minutes (lower and upper quartiles, -50 and 325) after CABG and 100 watt-minutes (-100 and 275) after PTCA. The degree of improvement did not differ between the two groups (P = 0.31).

The use of antianginal drugs was reduced in both treatment groups (Figure 2) in parallel with the symptomatic improvement. The patients in the CABG group used nitrates and calcium antagonists less frequently at 6 and 12 months than did the patients in the PTCA group. At one year, 22 percent of the patients in the CABG group and 12 percent of those in the PTCA group (P = 0.041) were not using any antianginal medication. There was no significant difference between the two groups in the use of aspirin (97 percent of the patients in the CABG group and 96 percent of those in the PTCA group used aspirin).


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  		Figure 2. Cumulative Percentages of Patients Using Antianginal Medication at the Time of Randomization and 6 and 12 Months after Treatment.

P values are for the comparison between treatment groups.

 
The rate of further interventions during the follow-up period disclosed another difference between the two procedures (Table 4). After discharge from the hospital, there were 71 additional interventions among the patients who had undergone PTCA as the initial treatment (45 underwent repeated PTCA, and 26 underwent CABG). Two or more subsequent interventions were necessary in 16 patients (PTCA in 9 and CABG in 7). In the first year CABG was necessary in 18 percent of the patients, repeated PTCA in 23 percent, and both in 3 percent. The overall rate of further interventions was 44 percent, and 21 percent of the patients initially treated with PTCA subsequently underwent CABG. In contrast, only six patients (4 percent) in the CABG group had subsequent angioplasty, and none had repeated CABG after discharge. The overall rate of further interventions in the CABG group was 6 percent (CABG, 1 percent; PTCA, 5 percent). Thus, 94 percent of the patients in the CABG group but only 56 percent of those in the PTCA group did not require further interventions (Figure 3).


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  		Figure 3. Rate of Further Interventions (CABG or PTCA) in the Two Treatment Groups during the Initial Hospitalization and 3, 6, and 12 Months Later.

 
A total of 219 patients (117 in the CABG group and 102 in the PTCA group) underwent coronary angiography six months after the initial intervention. These patients did not differ in clinical symptoms from those who refused follow-up angiography. Thirteen percent of the vein grafts in the CABG group were occluded, and 7 percent of the internal-thoracic-artery anastomoses did not function at six months. In the PTCA group, 16 percent of the revascularized vessels were occluded or markedly restenosed (>= 70 percent).

Discussion

Balloon angioplasty is widely accepted as a routine treatment in patients with symptomatic single-vessel coronary artery disease. To clarify the role of angioplasty as an alternative to bypass surgery in patients with symptomatic multivessel disease, several randomized trials have been undertaken22,23,24,25,26. The larger of these trials, such as the Randomised Intervention Treatment of Angina (RITA) trial22 and the Bypass Angioplasty Revascularization Investigation (BARI),26 were designed to investigate differences in mortality over a five-year period. The GABI trial, which was smaller, compared the effects of these two procedures on angina one year after complete revascularization. The interval of one year was considered adequate for evaluating recovery from open-heart surgery and for detecting early occlusion of bypass grafts27 and restenosis after angioplasty28. Unlike the RITA study,22 the GABI trial did not include patients with single-vessel disease.

Our results show that the two treatments were equally effective in relieving angina in the patient cohorts studied. Only during the first three months did patients in the CABG group report less angina than those in the PTCA group. One year after treatment, however, the proportion of patients who were free of angina was comparable in the two groups (CABG, 74 percent; and PTCA, 71 percent).

The clinical improvement was accompanied by an improved capacity for exercise, although in one quarter of the patients in both treatment groups the maximal workload was lower after treatment than it had been before treatment. In both groups the need for antianginal medication was reduced. Nitrates and calcium antagonists were prescribed less frequently after CABG than after PTCA, and more patients in the CABG group required no antianginal treatment at all.

The GABI trial was not designed to detect differences between CABG and PTCA with respect to major cardiac events or mortality. The larger RITA trial22 did not demonstrate any difference in these variables. In the present study, patients undergoing surgery had a higher rate of perioperative myocardial infarction and more frequent noncardiac complications. There was no statistically significant difference between the treatment groups with respect to procedure-related mortality. One year after randomization, 14 percent of the patients in the CABG group had died or had a myocardial infarction, as compared with 6 percent of those in the PTCA group (P = 0.017). However, this result must be interpreted in the light of the long interval between randomization and treatment, which was due to limited resources for performing the procedures, especially the surgery, in the participating centers during the period of randomization. Mortality during the waiting period, which was almost as high as that during the interventions, reflects the fact that the randomized patients had severe coronary disease requiring treatment without delay. When only the patients who actually underwent the assigned treatment were included in the analysis, the difference in mortality and major cardiac events was not as great (11 percent in the CABG group vs. 5 percent in the PTCA group, P = 0.047).

The rate of further interventions required to achieve a clinically acceptable result reflects a basic difference between the two treatment approaches. Complications of angioplasty led to urgent bypass surgery the same day in 2.8 percent of the patients in the PTCA group. This complication rate is in the range reported for single-vessel angioplasty29,30 and multivessel angioplasty5,6,7,8,9. In another 5.7 percent of patients in the PTCA group, bypass surgery was performed during the initial hospitalization. Among the patients randomly assigned to surgery, only two (1.2 percent) required repeated bypass grafting during hospitalization. After discharge, only 4 percent of the patients who initially underwent surgery required PTCA, resulting in an overall rate of further interventions of 6 percent. In contrast, by the end of the first year, 21 percent of the patients in the PTCA group had undergone subsequent surgery, and 26 percent had undergone repeated angioplasty of at least one vessel. Because 3 percent of the patients had undergone both procedures, the overall rate of further interventions was 44 percent in the PTCA group. This finding is consistent with the results of other studies of angioplasty in patients with multivessel disease5,6,7,8 and with the results of the RITA trial22.

A potential advantage of balloon angioplasty in multivessel disease is that it can be used to treat the specific lesion considered responsible for the patient's symptoms31. The European Coronary Angioplasty versus Bypass Revascularization Investigation (CABRI) addresses this therapeutic principle23. In the GABI trial the efficacy of complete revascularization was investigated, since this may have a more favorable long-term outcome32,33,34,35,36. The fact that more vessels were grafted by surgeons than were dilated by cardiologists reflects the conceptual difference between the two treatment approaches. Cardiologists performing angioplasty have an opportunity to take a last-minute look and, if necessary, revise their original decisions, whereas surgeons tend to use grafts for less stenosed arteries as well as for those with greater stenosis. At six months, however, the degree of revascularization appeared to be equivalent in the two treatment groups in our study.

Only 4 percent of all patients with multivessel disease who were screened for the GABI trial were randomized. Similar recruitment rates have been reported for other randomized interventional trials2,22. Many patients had to be excluded because of total occlusions or recent myocardial infarctions.

Although new techniques, such as atherectomy, rotational atherectomy, and the use of stents, were introduced during the recruitment phase of the trial, they still have only a minor role and have not been established as alternatives to balloon angioplasty or surgery30,37,38. Recent improvements in balloon-angioplasty equipment appear to have a greater influence on therapeutic decision making.

These results, combined with available information from other randomized trials, may contribute to a more objective and balanced decision-making process in the treatment of patients with multivessel disease39. However, there is latitude for decisions that take into account the patient's age, concomitant diseases, special risks, and personal preference. It remains to be shown how these midterm results will compare with the outcome 5 to 10 years after treatment.

Supported by a grant (01 ZJ 8804/7) from the Bundesministerium fur Forschung und Technologie, Bonn, Germany.

We are indebted to the referring physicians for their support in conducting this trial and to the patients who agreed to participate in it.


Source Information

From the Department of Cardiology (C.W.H., J.R., W.B.) and the Institute of Mathematics and Computer Science in Medicine (J.B.), University Hospital Eppendorf, Hamburg; the Division of Cardiology, Klinikum Bogenhausen, Munich (T.I.); and Medical Clinic II, University of Mainz, Mainz (H.-J.R.) -- all in Germany. Presented in part at the 66th Scientific Session of the American Heart Association, Atlanta, Nov. 8-11, 1993.Dr. Bleifeld is deceased.Study participants are listed in the Appendix.

Address reprint requests to Dr. Hamm at the Department of Cardiology, Medical Clinic, University Hospital Eppendorf, Martinistrasse 52, D-20246 Hamburg, Germany.

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Appendix

Centers and investigators participating in the GABI trial included the following: University of Hamburg -- C.W. Hamm (chairman), J. Reimers, W. Bleifeld (deceased), E. Engelstein, A. Schuchert, A. Cortes, C. Franke, K.-H. Kuck, W. Terres, T. Meinertz, P. Kalmar, H. Krebber, and J. Darup; the University of Mainz -- H.-J. Rupprecht, U. Dietz, J. Meyer, R. Erbel, H. Oelert, S. Trautmann, and S. Iversen; Klinikum Bogenhausen -- T. Ischinger, W. Delius, G. Riess, D. Antoni, R. Hacker, and M. Meudt; Deutsches Herzzentrum Munchen; University of Tubingen -- W. Voelker, K. Karsch, and L. Seipel; University of Wurzburg -- P. Schanzenbacher and K. Kochsiek; University of Aachen -- R. Uebis, M. Sigmund, and P. Hanrath; and Staedtische Klinik Kassel -- H. Schmitt and K.-L. Neuhaus; Statistical Center: University of Hamburg -- M. Supplieth, J. Berger, and G. Lunstedt; Coronary Angiography Core Laboratory: University of Mainz -- H.-J. Rupprecht, U. Wenderoth, and J. Meyer.


 

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